Older, more established FCC catalyst regeneration techniques are operated in an incomplete mode of combustion. This invention is concerned with such modes of operation. These systems are usually referred to as "standard regeneration" wherein a relatively large amount of coke is left on the regenerated catalyst which is passed from an FCC regeneration zone to an FCC reaction zone. The content of CO in the regeneration zone is relatively high, i.e., 1 to 6 volume percent. The concentration of carbon is approximately 0.25 to 0.45 weight percent carbon on the regenerated catalyst. In U.S. Pat. No. 4,435,282, issued to Bertolacini et al, a system for substantially complete combustion of coke on an FCC molecular sieve catalyst is disclosed. In the regenerator, hydrocarbon conversion catalyst particles are associated with particles of a platinum group metal, an oxidation catalyst, which promotes the combustion of carbon monoxide to carbon dioxide. The gaseous effluent from such a regeneration run in a "full combustion mode" has a low CO content and a high content of carbon dioxide. The catalyst particles in an FCC process are finely divided particulate solids having a size of between 20 microns and 150 microns to insure adequate fluidization. U.S. Pat. Nos. 4,153,535, 4,221,667, and 4,238,371 issued to Vasalos et al concern the operation of a cyclic, fluidized, catalytic cracking process with a reduction in the emission of CO and SO.sub.x. A metallic promoter is incorporated into a molecular sieve-type cracking catalyst such that a stable sulfur-containing compound forms on the solid particles in the regeneration zone and a sulfur-containing gas is then withdrawn in a downstream sulfur stripping zone.
Nitrogen sensitivity of a hydrocracking catalyst has been found to be negated by introducing into the hydrocracking zone a halogen-containing compound and water with the hydrocarbonaceous feed. See Stine et al, U.S. Pat. No. 3,058,906. A number of U.S. patents issued to Chevron in the late 1970's and early 1980's concern catalytic conversion of nitrogen oxides to thereby control the nitrogen oxide levels in a flue gas generated by a catalyst regenerator.
In U.S. Pat. No. 4,204,945, a process is disclosed for removal of carbon monoxide and sulfur oxides from a flue gas of a catalyst regenerator of an FCC system. Sufficient molecular oxygen is introduced into the catalyst regenerator to provide an atmosphere having a molecular oxygen concentration of at least 0.1 volume percent. A particular carbon monoxide combustion promoter is physically admixed with the cracking catalyst to provide for total consumption of the coke to CO.sub.2. Sulfur oxides in the regenerator off gas are contacted with a silica-free alumina to form a sulfur-containing solid on the catalyst and thereafter hydrogen sulfide in the cracking reactor. In U.S. Pat. No. 4,204,944 issued to the same patentees, Flanders et al, a process is provided for an FCC unit having a non-zeolitic crystalline refractory inorganic oxide catalyst. The amount of carbon monoxide and sulfur oxides in the regenerator flue gas is reduced by reacting carbon monoxide and oxygen to carbon dioxide in the presence of a carbon monoxide oxidation promoter, inclusive of platinum. Sulfur and an alumina-containing solid are present wherein sulfur trioxide is reacted with alumina and thereafter hydrogen sulfide is formed in the cracking zone by contact of the sulfur and alumina-containing solid with the hydrocarbon feed stream. Similar techniques are provided in U.S. Pat. Nos. 4,115,250 and 4,115,251, Flanders et al, for the reduction of pollution emissions using an alumina-containing catalyst in association with a CO oxidation promoter.
NO.sub.x is controlled in the presence of a platnium-promoted complete combustion regenerator in U.S. Pat. No. 4,290,878, issued to Blanton. Recognition is made of the fact that the CO oxidation promoters result in a flue gas having an increased content of nitrogen oxides. These nitrogen oxides are reduced or suppressed by using, in addition to the platinum CO oxidation promoter, iridium or rhodium. U.S. Pat. No. 4,368,057 teaches the removal of NH.sub.3 contaminants of gaseous fuel by reacting the NH.sub.3 with a sufficient amount of NO. This prior art has failed to appreciate a system whereby NO.sub.x is reduced by the control of ammonia in an incomplete combustion regenerator.